textproduct: Quad Cities

KEY MESSAGES

- Oppressively hot and humid through this evening, with heat indices in many locations peaking around 105-115 degrees.

- Thunderstorms are possible this afternoon into the evening, though there remains some uncertainty due to capping inversions. Some of these storms may be strong to severe with damaging winds the main hazard if well-organized convection develops. A Slight Risk (level 2 of 5) for severe weather remains for areas along and east of the Mississippi River.

- Some mid-week relief from the heat and humidity comes behind a cold front tonight, although smoke from Northwest U.S. and Canadian fires may spread over the area that could continue through Tuesday.

SHORT TERM /THROUGH TUESDAY/

Issued at 207 PM CDT Mon Jul 27 2026

Mid-day upper air flight shows several small capping inversions aloft. These caps, along with likely subsidence behind the MCS along Lake Michigan, are acting to suppress convective development across the area so far.

Peak heating along any boundaries or theta-e gradients should force isolated to low-end scattered (20-40%) coverage of diurnal storms along/ahead of the cold front. These storms will quickly dissipate with sunset, leaving the remainder of the overnight hours muggy but dry.

The question after midnight is will any smoke approach the surface due to post-frontal mixing or remain aloft. Some solutions suggest yes while others say no. So, we will do a middle of the road solution and do a partial mix-down with the idea some areas may experience some smoke for a few hours but a majority of it remains aloft.

Tuesday will be a bit cooler and definitely less humid, with dew points in the upper 60s to lower 70s. Net result will be peak afternoon heat indices in the upper 80s to lower 90s.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 202 PM CDT Mon Jul 27 2026

Tuesday night through Thursday will continue to be on the dry side, thanks to an area of high pressure/subsidence that's progged to develop over the western Great Lakes, along with an upper-level ridge over the Great Plains region. Temperatures will remain seasonably warm, with high temperatures forecast for Wednesday and Thursday in the middle to upper 80s, and nighttime lows in the middle 60s.

As we go through the day Thursday, the aforementioned upper ridge begins to break down, with a mid-level shortwave trough embedded in the zonal flow. A quasi vertically-stacked upper low will accompany the trough, which will help further support large-scale forcing over our region. Likely chances of showers and thunderstorms (50-70%) look to increase late Thursday night into Friday. At this time, strong to severe storm potential for this period appears to be pretty low, given meager instability and deep-layer shear magnitudes (20-30 knots). The latest machine-learning severe probs from NSSL, NCAR, and CSU all show very small values, if anything. More likely, this bout of precipitation appears to bring beneficial rainfall to the area, with the latest NBM exceedance probabilities of a half inch of total rainfall through 12z/7 AM Saturday around 40 to 60% across the area. With the precipitation and cooler air mass building in, temperatures look to be cool even further for the end of the week, with highs warming to around 80 degrees for Friday and Saturday - a welcomed sign for those looking for relief from the heat.

Saturday and Sunday: there could be some lingering chances of showers/storms Saturday morning before the aforementioned stacked upper low moves out and another high pressure system builds in, bringing drier conditions to the area.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1215 PM CDT Mon Jul 27 2026

The morning inversion has eroded but has been replaced by multiple capping inversions aloft. Thus convection will be suppressed until the caps can be over come; most likely during peak heating. Thus isolated to scattered (15-35%) coverage is possible along and ahead of the cold front from 20z/27 through 02z/28 across eastern Iowa and northern Illinois. After 02z/28 convection will dissipate but haze from wildfire smoke will be possible.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Extreme Heat Warning until 10 PM CDT this evening for IAZ040>042-051>054-063>068-076>078-087>089-098-099. IL...Extreme Heat Warning until 10 PM CDT this evening for ILZ001- 002-007-009-015>018-024>026-034-035. MO...Extreme Heat Warning until 10 PM CDT this evening for MOZ009- 010.